If you go into Dreamweaver and perform a search on all the pages in the PowerStore directory, you should find 3 places where the products_Search.php should be changed to Products_Search.php. That way you won't have to manually change it and then navigate there. Try making that change and then adding the products directly.
In the coupon system currently, there is no built in way to determine to add the coupon if there is over x number of items. You will have to use the value added to cart.